This work investigates a novel metamaterial concept using the Wave-based Finite Element Method. The metamaterial comprises a periodic-like structure manufactured through fused filament deposition, featuring internal cavities filled with water. Experimental characterization of the dynamics of the periodic system without internal fluid confirms good agreement with numerical predictions obtained through frequency response function measurements. Furthermore, the dynamic behavior of the two-phase periodic metastructure is experimentally examined, where waves interact within the heterogeneous medium consisting of both fluid and solid phases. In this case, the resulting wave characteristics depend on the properties of both phases. It was shown that the fluid-filled metastructure exhibits vibration reduction through the whole frequency range compared to the case lacking internal fluid. Additionally, it was seen that the frequency range near the second attenuation band of the periodic metastructure without fluid can be enlarged after the fluid inclusion within the cavities of its unit cells, as a consequence of mass increase and damping effects. Consequently, this work presents a promising avenue for metastructure design, with potential applications in structural dynamics and acoustics.